Pat the chicken dry, then place it in a large bowl. In a small bowl, stir the garlic powder, paprika, salt, oregano, and black pepper together, then pour the spices over the chicken and use your hands to completely coat the chicken.
Next, add the olive oil and butter to your Instant Pot, then press "saute" and set it for 6 minutes. Allow 2 minutes for the butter to melt; once the butter starts shimmering, place the chicken skin-side down into the pot and pan-sear it, undisturbed, for 3 minutes. Then, flip it over, add the minced garlic, and cook for 1 more minute.
Use kitchen tongs to remove the chicken, then pour in the chicken broth and use a wooden spoon to scrape up any brown bits from the bottom of the pot. Place the trivet into your Instant Pot, then lay the chicken skin side up onto the trivet (you should be able to perfectly fit 4 chicken thighs).
Place the lid onto your Instant Pot, ensuring the valve on top is in the "seal" position. Pressure cook the chicken on high pressure for 10 minutes, then natural release the pressure for 10 minutes before manually releasing the rest.
Carefully lift the trivet, along with the chicken, out of the pot. Next, whisk 1 tablespoon cornstarch and 1 ½ tablespoon water together in a bowl, then pour the paste-like mixture into the pot. Press "saute" and set it for 2 minutes, whisking occasionally to create the gravy.
Spoon the gravy over the chicken, then sprinkle everything with a little salt and pepper. Enjoy!